Automatic starter for electric motors



1953 B. ANTIPOVITCH 2,627,595

AUTOMATIC STARTER FOR ELECTRIC MOTORS Filed Dec. 2, 1950 I5 Sheets-Sheet l INVENTOR. BORIS ANTIPOVITCH.

@ flwa wwmap A; ATTORNEYS.

1953 B. ANTIPOVITCH 2,627,595

AUTOMATIC STARTER FOR ELECTRIC MOTORS Filed Dec. 2, 1950 3 Sheets-Sheet 2 A. AMPS vou's SWITCH A .L) -5w|Tc.H c IT|ME 5TART OPEN- CLOSED.

REACTOR core: 5 FIG. 5.

INVENTOR. BORIS ANTI POVITCH.

A6 ATTORNEYS.

Feb. 3, 1953 B. ANTIPOVITCH 2,627,595

AUTOMATIC STARTER FOR ELECTRIC MOTORS Filed Dec. 2, 1950 3 Sheets-Sheet 5 BORlb' ANTIPOVU'CH.

l4, ATTORNEYS.

Patented Feb. 3, 1953 UNITED.

ATES dTENT. OF CE Boris Antipovitch, Mexico City, Mexico.

Application December 2, 1950, Serial No. 198,813

" In Mexico January 20, 1.950

lzcl aims. (01.318-229) This invention relates toapparatus for starting an alternating-current motor on. reduced voltage and automatically transferring it to full voltage when it has come up to substantially normal speed. the apparatus disclosed in'myprio'r Patent No. 2,471,185.

The ohject of the present invention is to provide starting apparatus having provisionfor adjusting the voltage applied initially tothe motor windings and for achieving a closer control of the operation of transfer from starting to running voltage.

My improved starting apparatus comprises a multi-pole magnetic switch having series exciting windings, one for each phase, and an autotransformer with an open core adapted to closed by a movable armature when the core is sufiiciently excited. The auto-transformer has a plurality of windings, one for each phase, the primary portions of which are connected in scries with the windings of the magnetic switch. The latter has contacts controlling the autotransformer windings effective, to change their function from a series impedance to a true transformation. A contactor controlled by the switch shunts the windings of boththe switch and autotransfo'rmer when the motor is up to speed.

A complete understanding of the invention may heootained from the following detailed description and explanation thereof which refer to the accompanying drawings illustrating a preferred embodiment. In the drawings:

Fig. l is a circuit diagram showing the various ever-a1 elements of a poly-phase motor starter in outline and the connections therecetween;

Fig. 2 is a similar diagram showing a singlephase station;

Fig. 3 is a set oi curves showing the variation of motor current and applied voltage during the several steps of a starting cycle; and

Fig. l shows a. further modification oi the in vention particularly adapted for starting large motors.

Referring now in detail to the drawings, a inagnetic switc A has an E-shaped core i with a leg for each phase; a series winding 2 on each leg and an armature 3 adapted to be attracted into engagement with the core on excitation thereof. The windings are tapped for the purpose of adjustrnent. Armature 3 has projections it at the ends thereof and is normally held open by, springs 5 dispose between the projections and'adjustable abutments The switchis provided with fixed contacts '1 adapted to be engaged bymoving The invention is an improvementon 2 contacts 3 on the armature .whenthe latter is attracted to closed position. The switch also ineludes an auxiliary contact 9- which is closed when the armature is retracted, for apurpose which will appear later.

An auto-transformer B ane-shaped core 19 with secondary windings, l l on the legsthereof, one for each phase,.portions of which (the primaries) are connected in series with windings 2 of switch A.v The windings i! are tapped, to permit adjustment. and are connected to contacts l of switch A. The contacts 8 of switchn are connected together so that closing of the switch connects windings l l in their entirety.(the secondaries) in start. An armature, i2 is attracted by core it! when excited to close the mag netic circuit thereof, converting the device from a reactor to a true autotransformer. The armature has projections 12 at, the ends thereof. It is normally held against adjustable back stops ,i t by springs i5 disposed between the. projections and adjustable abutments It.

Contactor C includes fixed contacts H and movable contacts l8 cooperating therewith, actuated by a core l9 and an operating coil vZ0 therefor. The contactor, when actuated, connects a supply circuit 2! through aswitch 22 directly to motor. 23,.thus shunting theflwindings of switch A and auto-transformer B. The coil in of corn tactor C is connected across .tWo phases on the motor side of contacts .ll, (8, and is controlled by auxiliary contact 9 on switch A.

The operation of the apparatus will now be described assuming that all the parts are in the normal positions as illustrated. When it is desired to start the motor 23, all that is necessary is to close switch 2'2. This completes a circuit from the supply line 21 through, windings 2 of switch A and the (primary) portions of the windings H of auto-transformerB to the windings of motor The windings 2 and the (primary) portions of windings i I in circuit both act as series impedancesand reduce the/voltage applied to the motor windings. The current. is a maximum at start, and the voltage applied to the mo tor windings (line voltage minus IZ drop) is thus a minimum (see Fig. 3). The. motor. therefore starts slowly on reduced voltage.v

Starting current flowing. through windings excites the cor 1 and the latter attracts .125 ara mature 3 against the force of springs 5. Contacts 3 engage contacts I and thus connect the ent e windings H (the secondaries) in star across line 2 I, in series with drawings 2. windings I i there upon increase the excitation of core it sufiiciently- 3 to cause it to attract armature [2 against the force of springs l5. Auto-transformer B thereafter functions truly as such and no longer simply as a series impedances. It is accordingly applies an increased voltage to the motor causing it to accelerate further. The value of this increased voltage depends on the adjustment of the taps of windings ll.

As the motor accelerates, the current drawn by the windings thereof decreases because of the building up of the back E. M. F. A point is eventually reached, depending on the adjustment of the taps of windings 2, where the current through the latter is insuflicient to hold armature 3 against the force of springs 5. On

retraction of this armature, the opening of contacts 7, i3 restores auto-transformer B to its original condition, the windings ll serving only as series impedances, and armature 12 being retracted. Adjustable back stops l6 permit the desired reactance to be thus introduced into the circuit. The motor current will have decreased to such a value by this time, however, that the IZ drop in windings 2 and H will be such, that the voltage applied to the motor is higher than cne previously applied by the auto-transformer. That causes a further acceleration of the motor and decrease of the current. By that time the voltage on the motor is gradually building up because the voltage drop through the windings 2 and H is proportional to the current flowing through.

Retraction of armature 3 depends on the adjustinent of the taps of windings 2 and that of abutments 6. When it occurs, auxiliary contact 9 is closed, placing coil 20 of contactor C across two phases of the motor windings. The increased voltage applied thereto as already explained soon reaches a value sufiicient to operate contactor C and it closes its contacts 7, 8, shunting windings 2 and H, thereby placing the motor windings directly on the line ii for normal operation under load. Contactor C is a magnetic switch of ordinary construction. Such switches have the characteristic of operating within a narrow range of applied voltage, providing the voltage is increased slowly. This condition is fulfilled in my invention and it accordingly causes connection of the motor directly to the line at precisely the correct moment in the starting cycle.

When it is desired to stop the motor, switch 22 is opened. The motor immediately starts to decelerate and contactor C opens its contacts 17, i3 when the voltage between the phases of the motor windings falls below the hold-in value of the operating coil, thus restoring all conditions to normal, ready for another starting cycle.

The embodiment illustrated is designed for a three-phase motor but may be easily modified,

as will be understood by those skilled in the art of electrical control, to adapt it for motors operating on a different number of phases. Fig. 2 shows a starter for a single-phase motor, similar in all essential respects to Fig. 1, corresponding elements being designated by the same reference numeral with a prime afiixed.

Fig. 4 shows a modified form of the invention using a slightly different means for controlling the impedance of the auto-transformer reactor. The system there shown is quite similar to that of Fig. 1 except that switch A has additional pairs of cooperating back contacts 24 and 25, one pair for each phase, the contacts of. each pair being. closed when armature 3 is released, i. e.,

is in the position shown. In addition, autotransformer B" ha a closed magnetic circuit or core 2% with one leg for each phase. Tapped windings 21, one on each leg, have one end connected to contacts 7, respectively, of switch A. The other end of each winding is connected to windings 2 of switch A and thus the upper portions of windings 27 are placed in series with windings 2. Windings 28 on the legs of core 26 are connected in opposition to windings 21, one end of each being connected to One of the contact 25 and the other end to one of additional pairs of contacts 29 and 30 controlled by contactor C, and closed when contacts I? and i8 thereof are open.

The operation of the system of Fig. 4 is the same as that of the system of Fig. 1 except for the control of the impedance of auto-transformer B". Windings 28 are connected in star to the motor 23 when the system is de-energized, but the closing of switch 22 connects motor 23 to line 2! in series with windings 2 and the active portions of windings 27 and current flows through them and windings 28 as well. The initial energization of windings 28 reduces the impedance of windings 27 to a predetermined value but when armature 3 of switch A is attracted, the opening of contacts 26 and 25 de-energizes windings 2%, and the closing of contact i and 8 connects the secondary portions of windings 2'5 to the motor in star. As the current through windings 2 is reduced by acceleration of the motor, and armature 3 is retracted by springs 5, contacts 1 and 8 are opened and contacts 24 and 25 reclosed. Thus the secondary portions of winding 27 are disconnected and windings 22 are again energized. The difierential effect of windings 28 reduces the impedance of windings 2? and consequently the impedance drop therethrough with the result that a higher voltage is impressed across the motor, increasing the current through windings 28. As the motor current decreases, the impedance drop is reduced further and a still greater voltage applied to the motor and to windings 28 connected thereacross. The efiect of windings 28 increases and the im pedance drop decreases at a rate greater than the motor current decreases. When the applied voltage sumces to operate switch C, contacts 29 and 3% are opened before contacts l7 and iii are closed, thus preventing a short-circuit across windings 23. Windings 28 remain de-energized so long as switch C is operated. When switch 22 is opened, all the parts return to starting position.

The modification of Fig. 4 like that of Fig. 1, can be applied to a single-phase starter as well as the polyphase starter shown.

It will be apparent from the foregoing that the invention provides starting apparatus which is simple in construction yet certain in operation and capable of close adjustment as to the value of motor current at which the transfer from starting to running voltage occurs, and also as to the value of voltage applied to the motor Winding in the second stage of the starting operation, 1. e., after the armature of auto-transformer B has been at tracted.

I claim:

1. Apparatus for starting an alternating-cup rent motor comprising a magnetic switch including an open core, a series exciting winding thereon adapted to be connectedto a supply line, an armature cooperating with said core to close it and contacts closed on movement of the armature toward the core, an auto-transformer having an open core including an armature movable toward the core to close it and a secondary winding on the core including a primary portion connected in series with said first-mentioned winding and the motor, said contacts when closed connecting said secondary winding across said line and a contactor controlled by the voltage across the motor effective to shunt the winding of said switch and the primary portion of said autotransformer winding.

2. Apparatus for starting an alternating-current motor comprising a magnetic switch including an open core, exciting windings thereon adapted to be connected as series impedances to a supply line, an armature attractable by said core when excited, an auto-transformer having a core including an armature attractable thereby when excited and secondary windings on said core each including a primary portion connected in series with one of said first-mentioned windings, respectively, and the motor, said switch having contacts closed when its armature is attracted, effective to connect said secondary auto-transformer windings across said line.

3. Apparatus for starting an alternating-current motor comprising a magnetic switch including an open core, exciting windings thereon adapted to be connected as series impedances to a supply line and an armature attractable by said core when excited, an auto-transformer having a core including an armature attractable thereby when excited and secondary windings on said core each including a primary portion connected in series with said first-mentioned windings, respectively, and the motor, said switch having one set of contacts connected respectively to said secondary auto-transformer windings and another set of contacts connected together so that engagement of said two sets of contacts connects said secondary auto-transformer windings in star to said line through said switch windings.

4. Apparatus as defined by claim 2 characterized by a contactor effective to shunt all said windings and an auxiliary contact on said switch armature controlling said contactor.

5. Apparatus for starting an alternating-current motor comprising a magnetic switch having operating windings adapted to be connected to a supply line as series impedances, auto-transformer having an open core with an armature therefor and secondary windings thereon, a portion of each of which acting as a primary winding is connected in series with said first-mentioned I windings, respectively, as additional impedances, and contacts on said switch effective when closed to connect said secondary auto-transformer windings across said line through said switch windings.

6. Apparatus for starting an alternating-current motor comprising a magnetic switch having operating windings adapted to be connected to a supply line as series impedances, an auto-transformer having an open core with an armature therefor and secondary windings thereon, a portion of each of said windings serving as primary and connected in series with said first-mentioned windings, respectively, as additional impedances when the auto-transformer armature is retracted, and contacts on said switch effective when closed to connect said secondary auto-transformer windings across said line and cause said core to attract its armature, thereby converting it from an impedance to an auto-transformer.

'7. Motor-starting apparatus comprising an auto-transformer including an open core with an armature and secondary windings on the core, each having a primary portion, the transformer primary winding portions being connected to the motor to serve as series impedances when connected to a supply line, and a magnetic switch having operating windings connected in series with said primary winding portions, said switch being effective when closed to connect the full secondary windings of the auto-transformer across said line.

8. Apparatus for starting an alternating-current motor comprising a magnetic switch including an open core, series exciting windings thereon adapted to be connected to a supply line, an armature cooperating with said core to close it and contacts closed on movement of the armature toward the core, an auto-transformer having a secondary winding for each phase of the motor and a differential winding for each phase, each secondary winding including a primary portion connected in series with one of the windings of said switch and the motor, and a contactor controlled by the voltage across the motor, said contactor having front contacts shunting the windings of said switch and back contacts connecting said differential windings across the motor, said first-mentioned contacts when closed connecting said secondary windings across said line.

9. Motor-starting apparatus comprising an auto-transformer having secondary windings each including a portion serving as a primary winding, and a magnetic switch having operating windings connected in series with the primary winding portions, respectively, and the motor, said switch when closed connecting the secondary windings across a supply line, said autotransformer also having differential windings, and a contactor controlled by the voltage across the motor having front contacts shunting the switch windings and back contacts connecting said differential windings across the motor.

10. A starter for an alternating-current motor comprising a magnetic switch and an autotransformer, said witch having windings adapted to be connected to a current source, and contacts closed when said windings are energized, said auto-transformer having a core with secondary windings thereon each including a portion serving as primary winding and connected in series with said switch windings, respectively, and the motor, said contacts when closed completing the circuit including said switch windings, said secondary windings and said source, and a contactor controlled by said switch having an operating winding connected across the motor on opening of the switch, said contactor having contacts serving when actuated by said operating winding to shunt said switch and auto-transformer and connect said motor directly to said source.

11. Apparatus as defined by claim 10, characterized by said auto-transformer core being open and having a movable armature cooperating therewith.

12. Apparatus as defined by claim 11 characterized by said auto-transformer having differential windings, said switch and said contactor having back contacts effective when closed to connect said differential windings across said motorsoars ANTIPOVITCH.

No references cited. 

